Nicardipine hydrochloride ((±)-2-(benzyl-methyl amino) ethyl methyl 1,4-dihydro-2,6-dimethyl-4-(m-nitrophenyl)-3,5-pyridinedicarboxylate mono hydrochloride) is a calcium ion influx inhibitor useful for the treatment of cardiovascular and cerebrovascular disorders (see, e.g., U.S. Pat. No. 3,985,758). Nicardipine hydrochloride is currently sold in capsule form and in an injectable intravenous form. The capsule form is marketed as CARDENE® and is available as an immediate release oral capsule and as an extended release oral capsule. The injectable intravenous form of CARDENE® is marketed in glass ampuls suitable for intravenous administration following dilution in a compatible intravenous fluid, such as dextrose or sodium chloride (CARDENE® I.V.). Each milliliter of a CARDENE® I.V. ampul contains 2.5 mg nicardipine hydrochloride in water, 48.0 mg sorbitol, buffered to pH 3.5 with 0.525 mg citric acid monohydrate and 0.09 mg sodium hydroxide. For infusion, each milliliter of the diluted formulation contains 0.1 mg of nicardipine hydrochloride, with a variable pH due to the diluent selected by the end user. United States Reissue Patent No. RE. 34,618 (a reissue. of U.S. Pat. No. 4,880,823) describes an injectable composition of nicardipine hydrochloride that is stored in a light resistant brown ampul. U.S. Pat. No. 5,164,405 describes a buffered pharmaceutical composition containing nicardipine designed for parenteral administration, that is also stored in an ampul.
The requirement for diluting CARDENE® I.V. before use is associated with a number of disadvantages. One disadvantage is that the diluted solution is only stable for 24 hours at room temperature. Another disadvantage is that the pH of the diluted formulation varies depending on the choice of diluent. Since CARDENE® I.V. can be used under emergency conditions to control blood pressure, dilution of the concentrated ampul formulation consumes valuable time that could be used to treat a patient. Other disadvantages associated with the dilution step include the potential for contamination, dosage errors, and safety hazards associated with the use of glass ampuls.
The pharmaceutical compositions and methods described herein overcome these disadvantages. In particular, the ready-to-use, injectable formulations described herein are stable, allow medical personal to use prepared containers containing an injectable formulation off the shelf without additional preparation, avoid potential contamination problems, and eliminate dosage errors.